The Administrative (Admin) Core provides scientific and administrative leadership to ensure that the overall Center aims and the specific aims of the individual Cores are achieved. This Core fosters transdisciplinary[1] activities and synergy among investigators and projects, to create the new teams needed to address the Center's aims: meet the goals of the NHAS, further research translation, and incorporate the changing contextual factors influencing HIV prevention and care among substance users. Since fostering transdisciplinary research underlies many of the strategies of this Core, we will briefly distinguish it from similar terms: multidisciplinary research is based on bringing together different disciplines to address a problem, and interdisciplinary research has been defined as transferring knowledge from one discipline to another. In both of these models, researchers retain their discipline-specific framework.[2] While much of the work of the Center has fostered these two collaborative methods, we now focus on Transdisciplinary research, which enables individuals to operate outside of the boundaries and cultures of their own disciplines to inform each other's work and create a new joint understanding of the problem to be addressed.[1,2] This approach moves beyond the limitations of any single disciplinary framework to create new synergies across investigators and new approaches to conducting research on health issues.[3,4] It is particularly well-suited for addressing public health problems and health disparities[1,3] that require multi-level approaches, e.g., examination of individual and contextual influences on health.[2] As described in this Core, many opportunities for discussion and collaboration (e.g., seminars, trainings, mentoring) are provided to Center-affiliated investigators, who represent diverse disciplines. These opportunities for inter-professional education[5,6] will help encourage a transdisciplinary approach in the conduct of research. This Core will also coordinate the dissemination activities of CDUHR, to reach a wide range of audiences. Findings will be disseminated to researchers, service providers and policy makers. The Admin Core will operate with guidance from several sources: (1) Executive Committee, (2) Scientific Advisory Board, (3) Community Advisory Board, (4) Policy Advisory Board, and (5) the Center-affiliated investigators. The Core maintains an environment that supports the project research base, fosters collaboration, and promotes innovative research. There is a growing awareness of the importance of addressing the research environment and contextual factors to create and support the work of transdisciplinary research teams, including developing social cohesiveness and using participatory goal setting to enhance team productivity.[7] Restrictive hierarchical structures can be obstacles to transdisciplinary research, and multiple internal feedback opportunities should be encouraged.[3] Thus, the Center will continue to operate using an organizational structure (see Introduction, Figure 2) where input from all Core members, affiliated Investigators and advisory structures is sought to guide Center activities and policies.